When fighting against mobile targets with an anti-aircraft gun there are different methods for aiming. The most simple one, but also the least reliable, implies so-called direct aiming, in which the aiming operator judges, by experience, the lead angle and the offset angle during tracking of the target through a simple ring sight. The aiming is entirely manual. In order to improve such manual aiming of an anti-aircraft gun its barrel has been provided with gyros for measuring its angular rates that emit signals corresponding to the angular rates of the barrel in elevation and azimuth to a calculating unit which in turn emits control signals to an optical sight, the aiming line of which is controllable in relationship to the direction of the barrel of the anti-aircraft gun. The control signals have the object to control the sight in relationship to the firing direction, so that the aiming operator, by aiming at the target and simultaneously setting the firing direction in elevation and azimuth, shall bring about such lead and offset angles that a fired projectile will hit the target. As the gyros for measuring the angular rates are fixed to the gun, the measurement is disturbed by their movement together with the setting of the barrel, so that the method implies a dependent aiming line method.
The development of systems for fire-control of anti-aircraft guns comprises remote control of barrels from a central ranging unit from which the range to the target is determined and its velocity and track in an earthbound coordinate system, and with the aid of a calculating unit the anti-aircraft gun is remotely controlled by servo means, so that the lead and offset angles for the barrel are the correct ones for firing the projectile. The range determination in such a central ranging unit is carried out by radar or by a laser meter provided with a thoroughly gyro stabilized sight. Such equipment is expensive and complicated. The manual aiming of the barrel is completely eliminated in these fire-control systems, which apply an independent aiming line method.
As there are still several manually aimed anti-aircraft guns, which are not suited to rebuild for remote control, there is a demand for a sight for the application of an independent aiming line method for manually aimed anti-aircraft guns. This sight should be simple and reliable and should permit a high degree of hit precision. The object of the invention is thus to provide a sight of the type mentioned introductorily, which bears said desired features and, further, is so stable when aiming without gyro-stabilizing that the range determination can be carried out simply by a laser meter.
Such a sight is characterized, according to the invention, in that the ranging unit is separate, comprising a support, manually pivotable in elevation and azimuth, independent of the firing direction of the anti-aircraft gun. The sight can be designed in many ways, either carried by an operator or by a stand which can be located at a distance from the anti-aircraft gun, or be mounted on the barrel of the anti-aircraft gun. In one embodiment the support of the ranging unit is pivotable in elevation around a substantially horizontal first axis in a yoke intended to be carried and be turned in azimuth by an operator. Suitably the yoke is designed to be carried on the shoulders of an operator.
The embodiment just described, where an operator is presumed to carry the ranging unit, can be advantageous in many cases. Considering that the ranging unit is normally rather heavy, an embodiment may in some cases be preferable where the support is pivoted in elevation around an axis which is carried by a portable stand. The turnability in azimuth can be achieved by a bearing or by suspension in an elastic element like a strong rubber band. Even in this case it is presumed that an operator is present below the stand, handling same in elevation and azimuth.
One further embodiment shows advantages in some cases. In it the support of the ranging unit is pivoted in elevation and azimuth in a base which is firmly connected to the barrel of the anti-aircraft gun. In order to improve the possibilities for a safe aiming it is suitable to provide the support of the ranging unit with a handle, arranged to act upon the elevation and azimuth movement by reduction of movement when the operator acts upon the handle.
In the last mentioned embodiment the ranging unit is located, together with the first optical means, at a small distance from the aiming unit with its second optical means. Thus the calculating unit is suitably arranged to correct the angle difference between the aiming lines through the first and the second optical means, depending upon a signal given to the calculating unit, corresponding to the mutual positions of said optical means; but in the last mentioned embodiment this angle difference may be of negligible value in most cases, and in such cases need not be taken into account.